This invention relates to a ski boot toe binding to be attached on a ski.
In one type of known ski boot toe binding, a boot toe holding member is connected to a pivot means which has a roller adapted to be slidably engaged with a cam surface or a guide groove under spring force. In the event that an abnormal external force is applied to the boot toe, the roller slides along the cam surface or the guide groove against the spring force to displace the pivot means, as well as the toe holding member, to a boot toe releasing position.
In such a toe binding, however, a relatively high frictional resistance is produced when the roller slides along the cam surface or the guide groove. Accordingly, the displacement of the pivot means to the toe releasing position from the toe holding position and vice versa is not smooth. In addition, the power of restitution of the pivot means from a displaced position not reaching the toe releasing position to the original toe holding position, is largely decreased due to the frictional resistance and, therefore, it becomes difficult in such a toe binding to have a long critical restitution stroke which allows the pivot member to automatically return to the toe holding position when the force applied to the toe holding member is released.
One of the most important functions of a ski boot toe binding is to absorb an instantaneously applied shock which is not great enough to cause the skier's leg to break and to hold the ski boot to the binding, but which will release the ski boot rapidly when a severe shock is applied to the skier's leg for a relatively long time period. To achieve the above functions satisfactorily, it is said that a boot toe binding having high stock absorbing energy and strong power of restitution is desirable.
The shock absorbing energy of the binding is determined by functions of the critical restitution stroke and the critical releasing force, beyond which force the binding will be displaced to a boot toe releasing position.
Namely, if the critical releasing force of the bindings is made constant, the binding having longer critical restitution stroke has higher shock absorbing energy. On the other hand, if the critical releasing force of the binding is made higher beyond a certain value, the binding will not be released as desired and will cause the skier's leg to break. Therefore, the critical releasing force of the bindings cannot be greater than a certain value in practice, and it is desired to provide a binding having longer critical restitution stroke.
However, if the toe binding having high shock absorbing energy with an elongated critical restitution stroke does not have a strong power of restitution, the binding will not be able to attain the desired function and will be dangerous in skiing because it takes a relatively long time period before the toe holding member, slightly displaced by an unobjectionable shock, returns to the original toe holding position.
Thus, it is desired that toe binding has not only a longer critical restitution stroke, but also strong power of restitution.
In the known toe binding set forth above, the power of restitution is relatively weak and the critical restitution stroke is relatively short, due to the frictional resistance caused by the sliding engagement between the roller and the cam surface or groove, so that the shock absorbing energy of the binding is relatively low.
Apart from the known toe binding set forth above, another type of toe binding is provided as shown in Japanese Pat. No. 50-22457 in which a pair of links are pivotably connected at the forward ends thereof to a toe holding member, and at the rear ends thereof to a base plate and are urged by a spring to usually set the toe holding member to a toe engaging position.
However, in the boot toe binding of this type, since the toe holding member is operably connected to the base plate only by the pair of links, the degree of displacement of the toe holding member is relatively small and therefore, the critical restitution stroke thereof is short with the result that the shock absorbing energy of the binding is relatively low.